/* PeerCheckTasks - TimerTask that checks for good/bad up/downloaders.
   Copyright (C) 2003 Mark J. Wielaard

   This file is part of Snark.
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
 
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

package org.klomp.snark;

import java.util.*;

/**
 * TimerTask that checks for good/bad up/downloader. Works together with the
 * PeerCoordinator to select which Peers get (un)choked.
 */
class PeerCheckerTask extends TimerTask {
	private final long KILOPERSECOND = 1024 * (PeerCoordinator.CHECK_PERIOD / 1000);

	private final PeerCoordinator coordinator;

	PeerCheckerTask(PeerCoordinator coordinator) {
		this.coordinator = coordinator;
	}

	public void run() {
		synchronized(coordinator.peers) {
			// Calculate total uploading and worst downloader.
			long worstdownload = Long.MAX_VALUE;
			Peer worstDownloader = null;

			int peers = 0;
			int uploaders = 0;
			int downloaders = 0;
			int interested = 0;
			int interesting = 0;
			int choking = 0;
			int choked = 0;

			long uploaded = 0;
			long downloaded = 0;

			// Keep track of peers we remove now,
			// we will add them back to the end of the list.
			List removed = new ArrayList();

			Iterator it = coordinator.peers.iterator();
			while(it.hasNext()) {
				Peer peer = (Peer)it.next();

				// Remove dying peers
				if(!peer.isConnected()) {
					it.remove();
					continue;
				}

				peers++;

				if(!peer.isChoking())
					uploaders++;
				if(!peer.isChoked() && peer.isInteresting())
					downloaders++;
				if(peer.isInterested())
					interested++;
				if(peer.isInteresting())
					interesting++;
				if(peer.isChoking())
					choking++;
				if(peer.isChoked())
					choked++;

				// XXX - We should calculate the up/download rate a bit
				// more intelligently
				long upload = peer.getUploaded();
				uploaded += upload;
				long download = peer.getDownloaded();
				downloaded += download;
				peer.resetCounters();

				if(Snark.debug >= Snark.DEBUG) {
					Snark.debug(peer + ":", Snark.DEBUG);
					Snark.debug(" ul: " + upload / KILOPERSECOND + " dl: " + download / KILOPERSECOND + " i: "
							+ peer.isInterested() + " I: " + peer.isInteresting() + " c: " + peer.isChoking() + " C: "
							+ peer.isChoked(), Snark.DEBUG);
				}

				// If we are at our max uploaders and we have lots of other
				// interested peers try to make some room.
				// (Note use of coordinator.uploaders)
				if(coordinator.uploaders >= PeerCoordinator.MAX_UPLOADERS && interested > PeerCoordinator.MAX_UPLOADERS
						&& !peer.isChoking()) {
					// Check if it still wants pieces from us.
					if(!peer.isInterested()) {
						if(Snark.debug >= Snark.INFO)
							Snark.debug("Choke uninterested peer: " + peer, Snark.INFO);
						peer.setChoking(true);
						uploaders--;
						coordinator.uploaders--;

						// Put it at the back of the list
						it.remove();
						removed.add(peer);
					} else if(peer.isChoked()) {
						// If they are choking us make someone else a downloader
						if(Snark.debug >= Snark.DEBUG)
							Snark.debug("Choke choking peer: " + peer, Snark.DEBUG);
						peer.setChoking(true);
						uploaders--;
						coordinator.uploaders--;

						// Put it at the back of the list
						it.remove();
						removed.add(peer);
					} else if(peer.isInteresting() && !peer.isChoked() && download == 0) {
						// We are downloading but didn't receive anything...
						if(Snark.debug >= Snark.DEBUG)
							Snark.debug("Choke downloader that doesn't deliver:" + peer, Snark.DEBUG);
						peer.setChoking(true);
						uploaders--;
						coordinator.uploaders--;

						// Put it at the back of the list
						it.remove();
						removed.add(peer);
					} else if(!peer.isChoking() && download < worstdownload) {
						// Make sure download is good if we are uploading
						worstdownload = download;
						worstDownloader = peer;
					}
				}
			}

			// Resync actual uploaders value
			// (can shift a bit by disconnecting peers)
			coordinator.uploaders = uploaders;

			// Remove the worst downloader if needed.
			if(uploaders >= PeerCoordinator.MAX_UPLOADERS && interested > PeerCoordinator.MAX_UPLOADERS
					&& worstDownloader != null) {
				if(Snark.debug >= Snark.DEBUG)
					Snark.debug("Choke worst downloader: " + worstDownloader, Snark.DEBUG);

				worstDownloader.setChoking(true);
				coordinator.uploaders--;

				// Put it at the back of the list
				coordinator.peers.remove(worstDownloader);
				removed.add(worstDownloader);
			}

			// Optimistically unchoke a peer
			coordinator.unchokePeer();

			// Put peers back at the end of the list that we removed earlier.
			coordinator.peers.addAll(removed);
		}
	}
}
